The difference between B and C is the current gain. The VCF and VCA circuits may not perform correctly if you substitute one for the other.

Matching mainly affects temperature stability. These days, most transistors from the same batch will be fairly well matched. I've built the VCO, Moog VCF and VCA without matching and they all operated reasonably well, the VCO tuning is just sensitive to temp.

I would guess the noise is something else. Adjusting the 10k's is for dealing with different signal levels for different systems but shouldn't create significant noise, especially if you're using it with other Yusynth modules or any modules with levels close to 10Vpp._________________My synth build blog: http://gndsynth.blogspot.com/

I don't know why the second input isn't hooked up, maybe just not enough room on the panel for another level control knob. You should be able to hook it up just like the first input.

I wouldn't use a center detent pot for fine tune. If anything I think it would exacerbate the problem of being too sensitive since it will snap to center when you want it just slightly off center.

There are several ways you can reduce the sensitivity:
1. increase the value of the 3.3M resistor - roughly double would probably be good if you can find something suitable. Using that large of a resistor might be less desirable due to noise, but wouldn't hurt to try and see if it works for you.

2. Put resistors in series with one or both of the end lugs of the pot. For example 12.5k on each end or 25k on one end.

3. Connect one end of the pot to ground instead of V+ or V-.

Any one of these changes should reduce the range of the fine tune by roughly half making it less sensitive. You can adjust the resistor values as you wish to decrease the amount of range/sensitivity however much you want.

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